Plenty of suggestions so far on solid performing products at a nice price point to give ya what you're looking for. However, the enclosure and power will control how much rattling you do. 1 12 can cause some hell, although I know that's not what you're going for.

Edit: why not just run a single sa-8 or American Bass XD8? Should be enough for your goals, and the enclosure can be TINY, especially if you run it sealed. Virtually no loss of cargo space at all, depending on how you build it.